SEARCH · PubMed Health

Results for “NITRIC ACID”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 595 records · Page 33Linked to original sources

PubMed1991

Micro method of analysis for magnesium in myocardial biopsies.

We developed a single-stage technique involving a proteolytic enzyme (pepsin) for the solubilization of cardiac muscle to measure magnesium in tissue. This new method has been developed specifically for use with very small cardiac biopsy samples (less than 1 mg) obtained with modern myocardial biopsy forceps. Pepsin digestion of the tissue releases magnesium ions into solution and, after centrifugation and dilution with lanthanum chloride, the resulting supernate is suitable for analysis by atomic absorption spectrometry. Recovery of magnesium after a single digestion approaches 99%. In direct comparison studies of pepsin digestion and a traditional method involving nitric acid extraction, the pepsin digestion consistently yielded more magnesium. In contrast to traditional methods of tissue solubilization, pepsin digestion is well suited to extraction of magnesium from the small biopsy samples commonly presented for analysis in clinical practice.

Biopsy↗

PubMed2001

On the investigation of homeopathic potencies using low resolution NMR T2 relaxation times: an experimental and critical survey of the work of Roland Conte et al.

We have attempted to reproduce differences in low resolution nuclear magnetic resonance (NMR) T2 spin-spin relaxation times between homeopathically potentised and unpotentised Nitric acid (nit-ac) solutions previously reported by Conte, et al. Using similar instrumentation and experimental protocols, we have shown that it is likely that Conte's original results are attributable to experimental artifact originating in the glassware used for the manufacture of the NMR tubes.

Homeopathy↗

PubMedDate not supplied

[Structure and sorption properties of regenerated hemosorbent SCN].

Stepwise desorption of protein components from the hemosorbent SCN after hemoperfusion was studied, and their molecular weights were determined. It was found that hard alkaline regeneration and oxidation with nitric acid do not affect the hemosorbent structure, composition and potentiometric characteristics. The regenerated hemosorbent can be successfully used for adsorbtion of extraneous low- and medium-molecular weight components to clarify microbiological liquids.

Adsorption↗

PubMed2006

[Effects of selective extraction on microorganisms on biomembrane in natural water body].

By the methods of direct viable count and plate count, this paper studied the effects of different selective extractants on the bacteria, algae and protozoan on the biomembrane in natural water body. The results indicated that the stronger the extraction ability of selective extractant, the fewer the living microorganisms on the biomembrane after extraction. Compared with the control, the percentages of living microorganisms on the biomembrane were 27.6, 14.1 and 0.01, respectively, after extracted by hydroxylamine hydrochloride (0.01 mol x L(-1) NH2OH.HCl + 0.01 mol x L(-1) HNO3), sodium dithionite (0.4 mol x L(-1) Na2S2O4, pH 6.0), and acidified ammonium oxalate. Very few bacteria was left after extracted by nitric acid (15% HNO3), and no microorgariisms could be detected after extracted by H2O2/HNO3, suggesting that the use of selective extractants affected the activity of biomembrane. With the decreasing amount of microorganisms on the biomembrane after treated with selective extractants, the adsorption of heavy metals by the biomembrane was gradually depressed.

Bacteria↗

PubMed1987

An improved combined cholinesterase stain and silver impregnation method for quantitative analysis of innervation patterns in frog muscle.

The original method combining Karnovsky's cholinesterase stain and Bodian silver impregnation has been modified to stain both myelinated and unmyelinated axons and to reduce background staining. The improvements were obtained by adding nitric acid to a paraformaldehyde-acetone fixative and by carrying out the silver impregnation of axons in an alcoholic solution. The method is especially suitable for quantitative estimation of the different kinds of nerve sprouting as well as for study of the remodeling of neuromuscular junctions in normal and experimental frog muscles.

Animals↗

PubMed1993

A scanning tunnelling microscopy study of the formation and chemical activation of step defects on the basal plane of pyrolytic graphite.

Scanning tunnelling microscopy is used to monitor etching of the basal plane of highly orientated pyrolytic graphite by ozone, oxygen and nitric acid. These treatments are seen to produce numerous single and multilayer step defects. Subsequent modification of the graphite sheet edges flanking these cavities by cyanuric chloride, TiCl4 and other reagents is shown to activate the edges, thereby making them capable of covalently binding various molecules.

Acrylates↗

PubMed1994

GFAAS determination of selenium in infant formulas using a microwave digestion method.

A method for determining the selenium content of infant formulas is proposed. It includes wet digestion with nitric acid and hydrogen peroxide in medium pressure teflon bombs in a microwave oven and determination by graphite furnace atomic absorption spectrometry (GFAAS). The absence of interferences is checked. Values obtained for the limit of detection (19.4 ng/g), precision (RSD = 2.2%) and accuracy by analysis of a reference material show that the method is reliable.

Humans↗

PubMed1990

Potato growth and yield using nutrient film technique (NFT).

Potato plants, cvs Denali and Norland, were grown in polyvinyl chloride (PVC) trays using a continuous flowing nutrient film technique (NFT) to study tuber yield for NASA's Controlled Ecological Life Support Systems (CELSS) program. Nutrient solution pH was controlled automatically using 0.39M (2.5% (v/v) nitric acid (HNO3), while water and nutrients were replenished manually each day and twice each week, respectively. Plants were spaced either one or two per tray, allotting 0.2 or 0.4 m2 per plant. All plants were harvested after 112 days. Denali plants yielded 2850 and 2800 g tuber fresh weight from the one- and two-plant trays, respectively, while Norland plants yielded 1800 and 2400 g tuber fresh weight from the one- and two-plant trays. Many tubers of both cultivars showed injury to the periderm tissue, possibly caused by salt accumulation from the nutrient solution on the surface. Total system water usage throughout the study for all the plants equaled 709 liters (L), or approximately 2 L m-2 d-1. Total system acid usage throughout the study (for nutrient solution pH control) equaled 6.60 L, or 18.4 ml m-2 d-1 (7.2 mmol m-2 d-1). The results demonstrate that continuous flowing nutrient film technique can be used for tuber production with acceptable yields for the CELSS program.

Culture Media↗

PubMedDate not supplied

Determination of lead in botanicals/Chinese prepared medicines by using microwave digestion with flow injection-inductively coupled plasma-mass spectrometry.

A simple, sensitive, and rapid method was developed for the determination of lead in botanicals and Chinese prepared medicines (CPM) by using closed-vessel microwave digestion with flow injection-inductively coupled plasma-mass spectrometry. The limits of detection and quantitation for the method, based on 0.5 g digested sample, were calculated to be 0.10 and 0.61 mg/kg, respectively. A simple approach was proposed for calibration by multiple linear regression (MLR) with 207Pb, 206Pb, and 204Pb for the determination of lead in botanical and CPM samples. The results from calibration by MLR were compared with those obtained by conventional modes using 207Pb and the sum of 207Pb and 206Pb. The results obtained by the different modes of calibration were in good agreement for botanical and CPM samples. The method was found to have good accuracy for the analysis of botanical reference materials. Method precision based on analyses of different types of CPM samples by different analysts on different days for different levels of lead was between 3.0 and 8.0% (relative standard deviation, n = 6). The effect of possible matrix interference caused by nitric acid and the extent of digestion was investigated with the method of standard additions. Significant matrix interference was not observed for the CPM samples analyzed. MLR was used to examine the effect of variation in isotopic abundance, which was found to present no significant problem in the determination of lead in the botanical and CPM samples.

Calibration↗

PubMed2006

Evaluation of ozone-nitrogen oxides-volatile organic compound sensitivity of Cincinnati, Ohio.

Ambient concentrations of ozone (O3), nitrogen oxides (NOx), total reactive nitrogen (NOy), nitric acid (HNO3), and hydrogen peroxide (H2O2) were measured during September 2003 at an urban site of Cincinnati, OH. The aim of this study was two-fold: to investigate whether O3 formation in this population exposure-type site is NOx, sensitive or volatile organic compound (VOC) sensitive and to test the practicality of using two combined observational-based methods to identify the sensitivity of O3 formation in midlevel polluted locations. The evaluation of the indicator species: NOy, O3/NOy, O3/HNO3, H2O2/ HNO3, and O3/(estimated NOx reaction products), as well as the combined hypothesis testing analysis of the weekend/weekday (WE/WD) differences of 1-hr and 8-hr average maximum O3 and of the 6:00 a.m.-9:00 a.m. average nitric oxide and NOx concentrations, show evidence that Cincinnati is likely VOC sensitive. Average WE 1-hr and 8-hr maximum O3, as well as duration of WE O3 accumulation, were not lower than the corresponding WD levels in spite of the observed significant reduction in NO, emissions on WE, a typical situation in VOC-sensitive locations. The possibility that the seasonal transition from summer to autumn could have influenced the results was also investigated through an exploratory analysis of the afternoon O3 maximum/NOx measured and of the WE/WD differences of peak O3 and morning average NO and NO, concentrations observed at this site from June through September 2003. The results suggest that a VOC-sensitive chemistry regime dominated along the summer season. The findings of this study suggest that additional reductions in regional NO, emissions in Cincinnati, a potential nonattainment area under the 8-hr O3 standard, may cause an increase in local O3. Future strategies to reduce O3 in Southwest Ohio should be further evaluated carefully. The combination of observational-based methods might provide a consistent complementary approach in the identification of the NO,-VOC sensitive characteristics of mid-to-moderate polluted urban areas.

Air Pollutants↗

PubMed1991

Effects of ferric and aluminum oxalates on dentin permeability.

The purpose of this study was to compare the efficacy of ferric oxalate, aluminum oxalate, or Tenure dentin conditioner, a marketed product containing aluminum oxalate, at reducing the permeability of human dentin in vitro. Topical treatment with these acidified agents or 2.5% nitric acid for 10, 30, or 60 seconds was compared. The results indicate that 10-second treatments of dentin with all agents increased dentin permeability. Extending the treatment to 30 seconds produced a decrease in dentin permeability for acidified aluminum and ferric oxalate with 60-second treatments being even more effective. Treatment with Tenure dentin conditioner for 60 seconds did not reduce dentin permeability as well as treatment with the other oxalate salts.

Dentin Permeability↗

PubMed2000

Speciation of antimony(III) and antimony(V) in cell extracts by anion chromatography/inductively coupled plasma mass spectrometry.

An analytical method for the separation and quantification of Sb(III) and Sb(V) using anion chromatography with ICP-MS is presented. The optimum conditions for the separation of the antimony species were established with 15 mmol/L nitric acid at pH 6 as eluent system on a PRP-X100 column. The retention times for antimony(V) and antimony(III) were 85 s and 300 s with detection limits of 0.06 microg/L and 0.29 microg/L, respectively. The proposed method was applied to cell extracts of Leishmania donovani, which were incubated with antimony(III) and antimony(V). Some metabolism seemed to occur within the cells.

Animals↗

PubMed2001

Evaluation of a photoacoustic detector for water vapor measurements under simulated tropospheric/lower stratospheric conditions.

Although water vapor is one of the most important and certainly the most variable minor constituent of the atmosphere, accurate measurements of p(H20) with high time resolution are difficult, particularly in the cold upper troposphere/lower stratosphere. This work demonstrates that a diode laser-based photoacoustic (PA) water vapor detector is a viable alternative to current water vapor sensors for airborne measurements. The PA system was compared with a high-quality frost point hygrometer (FPH) and with a Lyman-alpha hygrometer in the pressure range of 1000-100 hPa at frost point temperatures between 202 and 216 K. These conditions were simulated in a large environmental chamberfor 14 h. Simultaneous measurements with the three instruments agreed within 6%. Nitric acid vapor interferes with the FPH measurements at low frost point temperatures but does not affect the other instruments. The sensitivity of the PA system is already sufficient for measurements in the upper troposphere, and straightforward improvements can extend its useful range above the tropopause. Rugged construction, extreme simplicity, small size, and potential for long-term automatic operation make the PA system potentially suitable for airborne measurements.

Acoustics↗

PubMed1996

Change in trabecular architecture as measured by fractal dimension.

The objective of this work was to expose dried trabecular bone material to a decalcifying environment and to quantify the change in the spatial distribution of the bone with a fractal measure. Digitized radiographic images were produced from four separate slices of human vertebral bone as they dissolved within a solution of nitric acid. Pixel data from a region of interest (ROI) within the trabecular bone were used to estimate the time-dependent change in fractal dimension of the ROI as the bone dissolved. Results demonstrated that a change in the spatial distribution of trabecular material may be expressed in terms of a concurrently changing estimate of the fractal dimension.

Algorithms↗

PubMed2001

Optimisation of the storage of natural freshwaters before organotin speciation.

The speciation of organotin compounds is essential due to the species-dependent toxicity, especially in natural waters. Precautions have to be taken during sampling and storage of waters in order to prevent degradations and losses. Experimental design methodology has been used to study the conditions of stability of organotins after water sampling in rivers. The modelling of results allows the determination of optimal conditions of preservation. After acidification at pH = 4 with nitric acid, the storage in polyethylene containers at 4 degrees C in the dark is suitable to preserve the most degradable trisubstituted (butyl- and phenyl-) species over 1 month. These conditions of sampling and storage are applied to two different freshwaters. The rate of species decomposition appears to be only dependent on the water nature, whatever the organotin concentrations in the sample. Speciation could be so preserved between 1 and 3 months.

Chromatography, Gas↗

PubMed1999

Determination of total arsenic concentrations in nails by inductively coupled plasma mass spectrometry.

The analysis of trace elements in biological samples will extend our understanding of the impact that environmental exposure to these elements has on human health. Measuring arsenic content in nails has proven useful in studies evaluating the chronic body burden of arsenic. In this study, we developed methodology with inductively coupled plasma-mass spectrometry (ICP-MS) for the determination of total arsenic in nails. We assessed the utility of the washing procedures for removing surface contamination. Four types of preanalysis treatments (water bath, sonication, water bath plus sonication, and control) after sample decomposition by nitric acid were compared to evaluate the digestion efficiencies. In addition, we studied the stability of the solution over 1 wk and the effect of acidity on the arsenic signal. Arsenic content in the digested solution was analyzed by using Ar-N2 plasma with Te as the internal standard. The results suggest that washing once with 1% Triton X-100 for 20 min for cleaning nail samples prior to ICP-MS analysis is satisfactory. Repeated measurement analysis of variance revealed that there was no significant difference among the various sample preparation techniques. Moreover, the measurements were reproducible within 1 wk, and acidity seemed to have no substantial influence on the arsenic signal. A limit of detection (on the basis of three times the standard deviation of the blank measurement) of 7 ng As/g toenail was achieved with this system, and arsenic recoveries from reference materials (human hair and nails) were in good agreement (95-106% recovery) with the certified/reference values of the standard reference materials. ICP-MS offers high accuracy and precision, as well as high-throughput capacity in the analysis of total arsenic in nail samples.

Arsenic↗

PubMed1999

Ion chromatography of nitrite at the ppb level with photometric measurement of iodine formed by post-column reaction of nitrite with iodide.

The difficulty in ion-chromatographic determination of nitrite in aqueous solutions containing a high concentration of chloride arises mainly from incomplete resolution of the peaks for these anions on the separation column whose efficiency is not high. A photometric measurement of iodine formed by a reaction of nitrite with iodide has been found to make it possible to determine, chromatographically, trace amounts of nitrite without any interference from chloride; chloride does not oxidize iodide to produce iodine. The proposed method was based on the separation of nitrite from matrix anions on a silica-based anion-exchange column with a 1.5.10(-3) M phthalate eluent (pH 5.0), followed by photometric measurement of the iodine (as triiodide) formed via a post-column reaction of the separated nitrite with iodide. The optimal conditions for the post-column reaction were established by varying the concentrations of iodide, copper(II) and nitric acid in a post-column-reaction solution and the length of a reaction tube. A calibration graph for nitrite, plotted as peak heights versus concentrations, was linear up to 1.50.10(-5) M (690 ppb). The detection limit, defined at S/N = 3, was 1.00.10(-7) M (4.60 ppb) nitrite. The presence of chloride ions up to 0.01 M did not give any interference to the determination of nitrite. This method was successfully applied to the determination of nitrite in lake water, river water, sewage works water and snow samples without any pretreatment.

Chromatography, Ion Exchange↗

PubMed2004

The determination of nickel(II) after on-line sorbent preconcentration by inductively coupled plasma atomic emission spectrometry using Borassus Flabellifer inflorescence loaded with coniine dithiocarbamate.

A procedure was developed for the determination of nickel(II) in water samples by inductively coupled plasma atomic emission spectrometry (ICP-AES) after preconcentration on coniine dithiocarbamate (CDC) supported by Borassus Flabellifer inflorescence. The sorbed element was subsequently eluted with 0.4M nitric acid and the acid eluates are analysed by ICP-AES. The influence of various parameters such as pH, flow rate of sample, eluent concentration, volume of the sample and volume eluent were investigated. Under the optimal conditions, nickel in aqueous sample was concentrated about 100-fold. Nickel recovery was obtained by the proposed method in range of 98.9-99.9%. This method is also applied for the analysis of spiked and natural water samples. The results provide strong evidence to support the hypothesis of an adsorption mechanism.

Alkaloids↗